The Boy Scouts’ motto is: Be prepared. Who knew it meant preparing to de fend themselves against union thuggery? Kids, pay attention: This is a teachable moment for all of you on power, politics and Big Labor’s culture of corruption.

At last week’s City Council meeting in Allentown, Pa., a top official of the local Service Employees International Union chapter ranted about 17-year-old Scout Kevin Anderson’s park-cleanup work. To earn an Eagle Scout badge, Anderson devoted some 200 hours to picking up trash and helping clear a 1,000-foot walking path with fellow members of Boy Scouts Troop 301 of Center Valley.

But SEIU’s Nick Balzano gave them hell instead of thanks. He asserted that “there is [sic] to be no volunteers” since his union members were laid off. He then issued a witch-hunt threat: “We’ll also be looking into the Cub Scout or Boy Scout who did the trails. We may file another grievance on that.”

Citing union rules, he gave the City Council, the Scouts and all potential volunteers an iron ultimatum: “None of them can pick up a hoe. They can’t pick up a shovel. They can’t plant a flower. They can’t clear a bicycle path. They can’t do anything. Our people do that.”

That’s right: Balzano was ready to bludgeon the Boy Scout because his gung-ho volunteerism posed a threat to the SEIU labor monopoly.

The outrageous display of Boss Balzano’s union protectionism provoked a national furor. SEIU headquarters in Washington immediately blamed “the disreputable Fox News and other right-wing outlets like Michelle Malkin’s accuracy-challenged blog” for the backlash. It also distanced itself from Balzano, denying that he’s a top union leader and dismissing his remarks as “unauthorized.”

Fact: Labor Department records from 2008 (the most recent filing) show that Balzano is no rogue rank-and-file member: He serves on the SEIU local’s executive board and has served as president.

Last June, union officials in Baraboo, Wis., filed a complaint against volun- teer firefighters who built sandbag barricades to protect the city from record flooding. They whined that city Department of Public Works employees should have been called first and demanded overtime pay (for work they didn’t do) to compensate them.

Yes, kids, the city was knee-deep in water and the government union got mad that other people scrambled to work together in an emergency to put sand in bags, save homes and help their neighbors.

Public-sector unions aren’t about serving the public interest. They’re about serving their people, their power and their self-preservation.

In Montpelier, Vt., several years ago, the teachers union went after a superstar educator, Bill Corrow. The students, staff and supervisors at his school loved the social studies teacher. But the Vermont Education Association hated him because he was a volunteer who did not accept payment for his elective course.

Teachers unions are all for parents and schoolchildren volunteering their time to engage in political lobbying and power-expanding initiatives on the union’s behalf. But God help the community service-oriented individual with a passion for sharing his knowledge in their classrooms.

In California, union heavies in the Sacramento area sued a nonprofit environmental group for using college-age volunteers on a state-funded project to clean up a canyon and build a community trail. Big Labor dusted off an old law that requires volunteers to be paid prevailing wages for doing the cleanup. The law was finally repealed, but not without a brass-knuckles fight.

SEIU President Andy Stern in Washington speaks for all of Big Labor when he describes his organizing philosophy: “We prefer to use the power of persuasion, but if that doesn’t work, we use the persuasion of power.” President Obama, who has made national service an administration priority, has been and will continue to be silent about the Big Labor bullies who make public enemies of Scouts with trash bags and hoes.

You see, kids, Obama owes Stern (his most frequent White House visitor) and his union brethren. SEIU alone poured more than $60 million in compulsory membership dues into Obama’s campaign and leaned on its workers to “volunteer” to knock on doors, place phone calls and send out mailers for the Democratic Party. No good deed goes unpunished by union bosses — unless it benefits their political empire.